This invention relates to coating, adhesive and sealant compositions curable by Michael reaction, that is by addition of an anion derived from a nucleophilic group, for example a carbanion, to an activated carbon-carbon double bond. This involves reaction between (A) a Michael acceptor which is a compound or polymer generally containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least one and generally containing at least two nucleophilic groups.
Coating compositions curable by Michael reaction are disclosed in U.S. Pat. No. 4,408,018, GB-A-2048913, U.S. Pat. Nos. 4,602,061, 5,084,536, 5,169,979, EP-A-697444 and U.S. Pat. No. 4,730,013. In general, the Michael donor in these compositions is a compound having at least two activated methylene groups, for example acetoacetate groups, or a polyamine or polythiol.
U.S. Pat. No. 4,588,807 describes a benzylidenemalonic acid polyester and its use for the UV stabilisation of thermoplastics.
EP-A-599478 describes a coating or impregnating composition comprising an aqueous dispersion of a vinyl addition polymer and a reactive coalescent of the formula:
(CH3COCH2COO)xR or 
where R is an organic radical of valency x=1-6 and R1 is H or alkyl.
U.S. Pat. No. 5,451,653 describes improved crosslinking systems for coatings and adhesives comprising a crosslinkable polymer having activated ketomethylene (e.g. acetoacetate) groups and an aldimine curing agent.
U.S. Pat. No. 5,426,156 describes a two-component binder system comprising a CH-acid component that is a polymer with at least two enamine functions in the molecule and a compound containing at least two alpha, beta-unsaturated ester or amide groups.
Coating and Sealant compositions curing by Michael reaction have several advantages. Liquid polymers and oligomers can be crosslinked to form tough hard coatings, so that the coating composition need have little or no volatile organic solvent to achieve a viscosity suitable for spray application. The reactive groups involved in curing are less of a health and/or safety risk than most crosslinkable reactive groups. The cured materials are generally resistant to hydrolysis and degradation, particularly in the case where the Michael donor is an activated methylene group since the new bonds formed on crosslinking are Cxe2x80x94C bonds. Ester linkages, such as acetoacetates, acquire greater steric hindrance and hence hydrolysis resistance as a result of the Michael crosslinking reaction. The Michael reaction is beneficial for water-borne systems because it involves the transfer of hydrogen (as a proton) from a more electronegative element (with potential for hydrogen bonding) to a less electronegative element, carbon, which is not capable of hydrogen bonding. The reaction mixture therefore becomes less polar during curing, and in a coating the affinity for water should consequently decrease as curing progresses. In some cases, a water-soluble polymer/crosslinker system can be transformed into a water-resistant cured coating upon crosslinking. There is, however, a need for Michael curing coatings which cure more rapidly, particularly at ambient temperature, and/or are capable of curing without the need for powerful alkaline catalysts.
According to one aspect of the invention, a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a polymer having repeating units of the formula: 
where R is hydrogen or an alkyl or aryl group which is optionally substituted and R1 is hydrogen or an alkyl group which is optionally substituted;
X and X1 are each selected from an oxygen atom and a group of the formula 
where R1 is hydrogen or an alkyl or aryl group which is optionally substituted; and
A is a divalent organic group.
The alkyl groups mentioned above and throughout the remainder of the text may for example have up to 12 carbon atoms, preferably up to 4 or 6 carbon atoms, for example methyl or ethyl. The aryl groups mentioned above and throughout the remainder of the text may for example have 6 to 12 carbon atoms and are preferably phenyl. The alkylene and arylene groups referred to below and throughout the remainder of the text may be similarly defined except for being divalent instead of monovalent. Substituents for all such groups which may be mentioned are halogen, hydroxyl and other non-reactive groups. The divalent organic group A is linked to X1 through a carbon atom. It may for example be an alkylene or arylene group which is optionally substituted.
According to another aspect of the invention a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a compound or polymer containing at least two groups of the formula: 
where A1 is a divalent organic group or a linking bond whereby the group (II) is linked to the compound or polymer (A);
R3 is hydrogen or an alkyl group; and
E and E1 are each electron-withdrawing groups independently selected from groups of the formula: 
where R4 and R5 each represent an optionally substituted alkyl or aryl group and each group R6 represents a hydrogen atom or an optionally substituted alkyl or aryl group.
According to another aspect of the invention, a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a compound or polymer containing at least two groups of the formula: 
where R and R1 are defined as in formula (I) above and R46 is an alkyl or aryl group which is optionally substituted.
We have found that the polymers of formula (I), (II) or (XLV), in which the olefinic Cxe2x95x90C bond is doubly activated by having two electron-withdrawing groups on one of the carbon atoms at the Cxe2x95x90C bond, are substantially more reactive in Michael curing systems than are polymers containing acrylate or methacrylate ester groups.
According to another aspect of the invention, a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a compound or polymer containing at least two doubly activated olefinic groups of the formula: 
where R7 is an electron-withdrawing group, R8 and R9 are each independently selected from hydrogen, alkyl, which is optionally substituted, and aryl, which is optionally substituted; X2 is an xe2x80x94Oxe2x80x94 or 
where R10 is hydrogen or an alkyl group, and A2 is an optionally substituted alkylene group linking the doubly activated olefinic group to the compound or polymer (A); and in that the nucleophilic groups of the Michael donor (B) are beta-ketoamide groups of the formula: 
where at least one of the groups R11, R12 and R13 is an optionally substituted alkylene or arylene radical whereby the ketoamide group is linked to the compound or polymer (B) and the remaining groups R11, R12 and R13 are in the case of R11 
xe2x80x83an optionally substituted alkyl or aryl group and in the case of R12 and R13 a hydrogen atom or an optionally substituted alkyl or aryl group, provided that at least one of R12 and R13 is other than aryl and arylene; or
(ii) enamine beta-carboxylate groups of the formula: 
where at least one of the groups R18, R19 and R20 is an optionally substituted alkylene radical or R18 is an optionally substituted arylene radical, whereby the enamine beta-carboxylate group is linked to the compound or polymer (B), and of the remaining groups R18 is a hydrogen atom or an optionally substituted alkyl or aryl group, R19 is a hydrogen atom or an optionally substituted alkyl group and R20 is an optionally substituted alkyl group.
The use of beta-ketoamide groups in Michael donors for curing coating systems is mentioned in U.S. Pat. Nos. 4,871,822, 5,084,536 and EP-A-697444 but is not suggested as being particularly useful in conjunction with Michael acceptors which contain doubly activated olefinic groups. We have found that the combination of a Michael donor having beta-ketoamide groups with a Michael acceptor having doubly activated olefinic groups provides a coating composition curable at ambient temperature many times faster than known Michael curing coatings, for example about 100 or even 1000 times faster than similar coatings based on acetoacetate groups and acrylate groups.
The use of enamine carboxylate groups in Michael donors is mentioned in U.S. Pat. No. 5,426,156 but is not suggested as being particularly useful in conjunction with Michael acceptors which contain doubly activated olefinic groups. We have found that the combination of a Michael donor having enamine beta-carboxylate groups with a Michael acceptor having doubly activated olefinic groups provides a coating composition which cures rapidly at ambient temperature without need for a basic catalyst.
According to a further aspect of the invention a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the nucleophilic groups of the Michael donor (B) are groups selected from:
(i) enamine amide groups of the formula: 
xe2x80x83where at least one of the groups R14, R15, R16 and R17 is an optionally substituted alkylene radical or one of the groups R14, R15 and R16 is an optionally substituted arylene radical, whereby the enamine amide group is linked to the compound or polymer (B), and of the remaining groups R14, R15 and R16 are hydrogen atoms or optionally substituted alkyl or aryl groups, provided that R14 and R15 are not both aryl or arylene groups, and R17 is a hydrogen atom or an optionally substituted alkyl group;
(ii) heterocyclic groups of the formula: 
xe2x80x83where R21 is a hydrogen atom or an optionally substituted alkyl group, Z is a trivalent radical completing a heterocyclic 5- to 7-membered ring and A3 is a radical of valency at least 2 or a linking bond whereby the heterocyclic group is linked to the compound or polymer (B);
(iii) heterocyclic groups of the formula: 
xe2x80x83where R22 is a hydrogen atom or an optionally substituted alkyl group, Z1 is a trivalent radical completing a heterocyclic 5- to 7-membered ring and A3 is defined as above;
(iv) heterocyclic groups of the formula: 
xe2x80x83where Z2 is a divalent radical completing a heterocyclic 5- to 7-membered ring and A4 is an optionally substituted alkylene radical whereby the heterocyclic group is linked to the compound or polymer (B);
(v) heterocyclic groups of the formula: 
xe2x80x83where R23 is a hydrogen atom or an optionally substituted alkyl group; R24 is a hydrogen atom or an optionally substituted alkyl or aryl group; Z3 is a trivalent radical completing a 5- to 7-membered heterocyclic ring and A5 is a radical of valency at least 2 or a linking bond whereby the heterocyclic group is linked to the compound or polymer (B);
(vi) heterocyclic groups of the formula: 
xe2x80x83where R23 is a hydrogen atom or an optionally substituted alkyl group; Z4 is a divalent radical completing a 5- to 7-membered heterocyclic ring and A6 is an optionally substituted alkylene or arylene radical or a linking bond whereby the heterocyclic group is linked to the compound or polymer (B);
(vii) heterocyclic groups of the formula: 
xe2x80x83where X3 is an oxygen or sulphur atom; 
xe2x80x83where R25 is a hydrogen atom or an optionally substituted alkyl group; Z5 is a trivalent radical completing a 5- to 7-membered heterocyclic ring; and A7 is a radical of valency at least 2 or a linking bond whereby the heterocyclic group is linked to the compound or polymer (B);
(viii) heterocyclic groups of the formula: 
xe2x80x83where X5 is an oxygen or sulphur atom; R26 is a hydrogen atom or an optionally substituted alkyl group; and A8 is an optionally substituted alkylene group whereby the heterocyclic group is linked to the compound or polymer (B);
(ix) thio-containing ester or lactone groups of the formula: 
xe2x80x83where R27 is a hydrogen atom or an optionally substituted alkyl or aryl group and R28 is an optionally substituted alkyl group or R27 and R28 together form an optionally substituted alkylene linkage completing a lactone ring and A9 is an optionally substituted alkylene or arylene group whereby the thio-containing ester or lactone group is linked to the compound or polymer (B), or R29 is an optionally substituted alkyl or aryl group and A10 is an optionally substituted alkylene or arylene group whereby the thio-containing ester group is linked to the compound or polymer (B);
(x) phosphonite esters of the formula: 
xe2x80x83where R30 is an optionally substituted alkyl or aryl group, R31 is an optionally substituted alkyl group and A11 is an optionally substituted alkylene group whereby the phosphonite ester group is linked to the compound or polymer (B) or R31 and A11 are joined to form an optionally substituted alkylene linkage which completes a cyclic phosphonite ester ring, which alkylene linkage is substituted by a chemical linkage to the compound or polymer (B); A12 is an optionally substituted alkylene or arylene group whereby the phosphonite ester group is linked to the compound or polymer (B) and the groups R32 are each optionally substituted alkyl groups which are the same or different or are joined to form a heterocyclic ring; and
(xi) phosphinite esters of the formula:
(R33)2xe2x80x94Pxe2x80x94OA13xe2x80x94TM (XVIII)
or

xe2x80x83where each group R33, which may be the same or different, is an optionally substituted alkyl or aryl group; A13 as an optionally substituted alkylene group whereby the phosphinite ester group is linked to the compound or polymer (B) or one of the groups R33 and A13 are joined to form an optionally substituted alkylene linkage which completes a cyclic phosphinite ester ring, which alkylene linkage is substituted by a chemical linkage to the compound or polymer (B); A14 is an optionally substituted alkylene or arylene group whereby the phosphinite ester group is linked to the compound or polymer (B); R34 is an optionally substituted alkyl group and R35 is an optionally substituted alkyl or aryl group or R34 and R35 are joined to form a heterocyclic ring.
We have found that Michael donors containing groups of any of the formulae (IV) to (XIX) are substantially more active in Michael curing coatings than are the acetoacetates described in U.S. Pat. No. 4,408,018 and GB-A-2048913, the malonates described in U.S. Pat. No. 4602061 or the amines described in U.S. Pat. No. 4,730,033 and are capable of giving more rapid curing at ambient temperature and/or curing with less powerful alkaline catalysts. No base catalyst is required when using Michael donors containing thio-containing ester or lactone groups of formula (XIV) or (XV) or phosphonite or phosphinite esters of formulae (XVI) to (XIX).
The polymer having repeating units of formula (I) can for example be a polyester in which the groups X and XI represent oxygen atoms or a polyamide in which the groups X and X1 represent groups of the formula: 
where R2 is hydrogen or an alkyl group. Polyesters can for example be synthesised from a di(lower alkyl) malonate such as dimethyl malonate by either of two different routes, as illustrated in the following reaction scheme: 
in which Me=methyl, R is a monovalent aliphatic or aromatic group or hydrogen and A is a divalent aliphatic group.
The first route (1 and 3) uses the synthesis of dimethyl alkylidenemalonate from dimethyl malonate and an aldehyde RCHO by the Knoevenagel reaction (Reaction 1). Reaction 3 gives the polyester oligomer by a transesterification polymerisation reaction of the alkylidenemalonate with a diol HOxe2x80x94Axe2x80x94OH.
The second route (2 and 4) uses the synthesis of a malonate polyester oligomer from dimethyl malonate and a diol (Reaction 2). Reaction of the oligomer with an aldehyde by the Knoevenagel reaction produces the doubly activated double bond on each malonate site (Reaction 4). Malonyl di(acid chloride) can be used in place of the dialkyl malonate ester in Reaction 2.
The Knoevenagel reaction can for example be carried out by the use of Dean and Stark apparatus where the starting aldehyde and malonate compound are refluxed in toluene with a base catalyst such as piperidine or morpholine and an acid catalyst such as benzoic acid or acetic acid. Water, the reaction co-product, is separated and collected in the Dean and Stark graduated tube. An alternative procedure uses a titanium tetrachloride tetrahydrofuran complex and pyridine or N-methylmorpholine as the respective acid and base catalysts. This reaction is carried out under nitrogen at around 0xc2x0 C. with stirring. These lower temperature reaction conditions are preferred, especially for lower boiling aldehydes.
The transesterification reaction (Reactions 2 and 3) is carried out at temperatures of up to 190xc2x0 C. with vigorous stirring. A nitrogen purge can be used to facilitate distillation of the methanol condensate. A Dean and Stark apparatus can be used to collect the condensate, the amount of methanol collected being indicative of the progress of the reaction. n-Butyltin chloride dihydroxide or titanium tetraisopropoxide can be used as catalyst for the reaction. The degree of polymerisation of the polyester oligomer is dependent on the relative quantities of dimethyl malonate or dimethyl alkylidenemalonate and diol. For example, oligomers synthesised by using a mole ratio of 10:9 malonate to diol would at completion give a theoretical degree of polymerisation n of 9 and in practice give values of n of 6 to 9. Polymers having 3 to 20, particularly 5 to 10, activated Cxe2x95x90C bonds and a molecular weight in the range 600 to 5000 are generally suitable as Michael acceptors in coating and sealant compositions according to the invention.
For use in coatings, the reactive oligomer preferably has a low Tg (xe2x88x9230xc2x0 C. to xe2x88x9280xc2x0 C.) and a viscosity of less than 1.5 Pa s (15 poise).
Suitable aldehydes for use in the Knoevenagel reaction (1 or 4) are acetaldehyde (R=CH3) formaldehyde (R=H) butyraldehyde (R=n-C3H7), isobutyraldehyde (R=i-C2H7), isovaleraldehyde (R=i-C4H9) and benzaldehyde (R=C5H5). The diol HOxe2x80x94Axe2x80x94OH is preferably a straight-chain alkanediol HO(CH2)mOH where m=2-10, for example propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol or decane-1,10-diol, although branched diols such as propylene glycol or neopentyl glycol or ether-containing diols such as diethylene glycol can be used.
The polymer having repeating units of formula I can alternatively be a polyamide. For example, a polyamide having repeating units of the formula: 
can be prepared by reaction of a di(lower alkyl) malonate or malonyl di(acid chloride) with a di(primary amine) H2NANH2 to form a polyamide followed by Knoevenagel reaction with an aldehyde RCHO or ketone RCOR1. Alternatively, a diisocyanate OCN-J-NCO can be heated with malonic acid to form a polyamide 
which can undergo a Knoevenagel reaction to introduce the activated Cxe2x95x90C bond. In the latter reaction, the steps can be carried out in reverse order, that is malonic acid can be reacted with an aldehyde or ketone in a Knoevenagel reaction and the resulting unsaturated dicarboxylic acid can be heated with a diisocyanate to produce a polyamide. Polyamides possess considerable hydrolytic stability, as well as good resistance to other substances such as hydraulic fluid. Advantage may also be taken of the affinity of amides for water; water can be used as a solvent, diluent or plasticiser in coating or adhesive compositions based on a polyamide having repeating units of formula XXI.
The compound or polymer containing at least two doubly activated olefinic groups of formula (II) can be prepared from a compound containing at least two glycidyl groups, such as the diglycidyl ether of bisphenol A or a glycidyl acrylate polymer, by reaction with a hydroxy-substituted aldehyde such as p-hydroxybenzaldehyde, which can optionally be further substituted, for example 4-hydroxy-3-methoxy-benzaldehyde, followed by Knoevenagel reaction with a beta-dicarbonyl compound, preferably a beta-diketone, as shown in the following reaction scheme: 
The beta-diketone 
can for example be benzoylacetone, alpha-thenoyltrifluoroacetylmethane, pivaloyl propionylmethane or bis(alpha-furoyl)methane. The resulting compound of formula (XXII) contains no ester linkages and is extremely resistant to hydrolysis.
The Michael acceptor of formula (XLV) containing at least two doubly activated olefinic groups can for example be a phosphonocarboxylate ester containing groups of the formula: 
where A2xe2x80x94 is the residue of a polyol A2xe2x80x94(OH)n. Such a Michael acceptor can be prepared by reacting the chloroacetate of a polyol, for example butane-1,4-diol bis(chloroacetate), with trialkyl phosphite to form the phosphonoacetate 
of the polyol, and then carrying out a Knoevenagel reaction with an aldehyde RCHO under the conditions described above. The compound or polymer of formula (XLVI) can alternatively be prepared by a transesterification reaction of a phosphonocarboxylate triester of the formula: 
where L is a lower alkyl group, for example a methyl or ethyl group, with a polyol such as 1,6-hexanediol or trimethylolpropane to prepare a polyol ester containing at least two 
groups, followed by a Knoevenagel reaction. Alternatively the phosphonocarboxylate triester can be reacted first with an aldehyde in a Knoevenagel reaction followed by transesterification with a polyol.
The compound or polymer of formula (XLV) can alternatively contain at least two groups of the formula: 
where R53 is an alkyl or aryl group which is optionally substituted. Such a polymer can for example be prepared by reaction of an acidic phosphonocarboxylate diester of the formula: 
with a compound or polymer containing at least two glycidyl groups, for example the diglycidyl ether of bisphenol A or hydrogenated bisphenol A, to prepare a polyol ester such as 
where Bp is a bisphenol A nucleus. This polyol ester can undergo a Knoevenagel reaction with an aldehyde RCHO to form a compound or polymer containing at least two groups (XLVII).
The polymer having repeating units of formula (I) or containing groups of formula (II) can for example be used in a coating, adhesive or sealant composition with a Michael donor in which the nucleophilic groups are thiol groups, for example 1,6-hexanedithiol, bis(2-mercaptoethyl)ether or pentaerythritol tetrakis(beta-mercaptopropionate), primary or secondary amine groups, for example diethylene triamine or an amine-tipped polyether, phosphite ester groups or active hydrogen groups of the formula Yxe2x80x94CHxe2x80x94Y1, where Y and Y1 are each selected from groups of the formula: 
xe2x80x94SO2Q, pyridyl or triazinyl, R39, R40 and Q each represent an alkyl or aryl group and each group R41 represents a hydrogen atom or an alkyl group. The Michael donor can for example be a material containing at least two acetoacetate groups, cyanoacetate groups or beta-diketone groups, for example a polymer of acetoacetoxyethyl methacrylate or trimethylolpropane tris(acetoacetate). The polymer having repeating units of formula (I) can alternatively be used with a Michael donor containing groups having any of the formulae (IV) to (XIX).
The beta-ketoamide groups of formula (IV) can be prepared by the reaction of primary or secondary amine groups with diketene as described in U.S. Pat. No. 4,871,822 or with tetrahydropyrantrione (acetone dicarboxylic anhydride) as described in J. Chem. Soc. C 1971 at p.2721 or by the reaction of amine groups with a cyclic acetone diketene adduct. A polyamine such as diethylene triamine or an amine-tipped polyether can for example be reacted with diketene or tetrahydropyrantrione to prepare a material containing at least two beta-ketoamide groups.
The enamine beta-carboxylate groups of formula (VI) can be formed by the reaction of beta-ketoesters such as acetoacetates with amines or ammonia at ambient or slightly elevated temperatures of up to 100xc2x0 C., particularly 20-100xc2x0 C. Higher temperature reaction of beta-ketoesters with amines or ammonia, for example at about 180xc2x0 C., forms beta-ketoamides. In general, a poly(acetoacetate) can be reacted with ammonia, or a monoamine or a polyamine can be reacted with an alkyl acetoacetate, to produce materials containing two or more enamine beta-carboxylate groups of formula (VI). The enamine beta-carboxylate groups need not be preformed. A compound containing at least two beta-ketoester groups, for example trimethylolpropane tris(acetoacetate), and a substantially non-volatile primary amine having at least 6 carbon atoms can be mixed to form a component of the coating composition. They will react at least partially to form enamine beta-carboxylate groups and will react further as the enamine beta-carboxylate groups are consumed in the Michael curing reaction. The enamine beta-carboxylate groups of formula (VI) can alternatively be formed by the reaction of an amine, for example a polyamine such as a di(primary amine), with an acetylenecarboxylate ester.
The material containing at least two beta-ketoamide groups, or the material containing at least two enamine beta-carboxylate groups, is used in a Michael curing coating, adhesive or sealant composition with a Michael acceptor which is a compound or polymer containing at least two doubly activated olefinic groups. The Michael acceptor can for example be a polymer containing repeating units of formula (I) or a compound or polymer containing at least two groups of formula (II) or (XLV). The electron-withdrawing groups of the Michael acceptor are preferably selected from xe2x80x94CN, acyl groups of the formula 
where R43 is an optionally substituted alkyl or aryl group, ester groups of the formula: 
where R44 is an optionally substituted alkyl or aryl group, imide groups of the formula xe2x80x94CON(R45 )2 where each group R45, which can be the same or different, is selected from hydrogen and optionally substituted alkyl or aryl, or a triazine group which is optionally substituted, a phosphonate ester group of the formula 
where R46 is an optionally substituted alkyl or aryl group, a sulphone group of the formula xe2x80x94SO2R47, where R47 is optionally substituted alkyl or aryl, or an alpha- or gamma-pyridyl group. The Michael acceptor can for example be prepared from a polyhydroxy compound Z6 xe2x80x94(A2OH)n where Z6 is a core radical of functionality (n) at least 2 and A2 is an optionally substituted alkylene group, by reaction with either an alkyl malonate diester such as dimethyl malonate to produce the poly(methyl malonate)ester 
or diketene or a diketene adduct to produce the poly(acetoacetate) ester 
followed in either case by a Knoevenagel reaction with an aldehyde RCHO to convert the active methylene group to a 
linkage. The polyhydroxyl compound can for example be trimethylolpropane, pentaerythritol or the oligomer octa-caprolactone tetrol sold under the Trade Mark CAPA 316 and having equivalent eight 262 g/mol and Tg xe2x88x9266xc2x0 C.
A dialkyl malonate such as dimethyl malonate can be reacted with a polyhydroxyl oligomer in a transesterification reaction at about one mole dimethyl malonate per hydroxyl group of the oligomer at temperatures of up to 180xc2x0 C. with stirring. An organometallic compound such as butyltin chloride dihydroxide is generally used as a catalyst for the reaction. The progress of the reaction can be followed by the amount of methanol co-product evolved.
The acetoacetylation reaction can be carried out using diketene or a cyclic diketene/acetone adduct such as 2,2,6-trimethyl-4H-1,3-dioxin-4-one. 
This compound decomposes when heated above 100xc2x0 C., for example at 120-180xc2x0 C., to provide acetylketene and acetone and readily reacts with hydroxyl groups by acetoacetylation.
The subsequent Knoevenagel reaction can be carried out under the conditions and using the aldehydes as described above, most preferably at 0xc2x0 C. using titanium tetrachloride tetrahydrofuran complex and pyridine as the respective acid and base catalysts.
The Michael acceptor containing at least two doubly activated olefinic groups can alternatively be a triazine compound of the formula: 
where R48 is hydrogen or an alkyl or aryl group. Such a triazine compound can be prepared from cyanuric chloride by the following reaction scheme: 
The enamine amide groups of formula (V) can be formed by the reaction of beta-ketoamide groups with primary amine groups. For example, a polyamine of the formula Z7xe2x80x94(R17NH2)n, where Z7 is a core radical of valency n, for example a diamine such as hexamethylene diamine, can be reacted with a beta-ketoamide of the formula: 
under the conditions described in U.S. Pat. Nos. 4,089,845 and 4,161,580. Alternatively, a compound or polymer containing beta-ketoamide groups, prepared as described above, can be reacted with an amine of the formula R17NH2.
The heterocyclic groups of formula (VII) can for example be cyclic beta-ketocarboxylic amide groups such as pyrrolidindione groups of the formula: 
These can be formed by the reaction of an amine, for example a polyamine of the formula A3(NH2)n such as hexamethylene diamine, with 2,2-dimethyl-6-bromomethyl-1,3-dioxen-4-one (the bromination product of (XXIII)) with elimination of acetone.
The heterocyclic groups of formula (VIII) can for example be amino-substituted pyrrolinone groups of the formula: 
which can be formed from pyrrolidindione groups of formula (XXV) by reaction with an amine R22NH2.
The heterocyclic groups of formula (IX) can for example be cyclic enamine beta-carboxylate ester groups such as 4-aminofuranone groups of the formula: 
or cyclic enamine beta-carboxylic amide groups such as 4-aminopyrrolinone groups of the formula: 
where R49 is hydrogen or an alkyl or aryl group. The 4-aminofuranone groups of formula (XXVII) can for example be prepared by reaction of a polyamine A4(NH2)n with furan-2,4-dione or a gamma-chloroacetoacetate ester. The 4-amino-pyrrolinone groups of formula (XXVIII) can be prepared by reacting a polyamine A4(NH2)n with a pyrrolidindione.
The heterocyclic groups of formula (X) or (XI) can for example be pyrazolone groups of the formula: 
where R50 is a hydrogen atom or an alkyl or aryl group, or tetrahydro-1,4-diazepin-5-ones of the formula (XXXI) or isoxazolones of the formula (XXXII) 
The pyrazolone groups can readily be synthesised by reaction of hydrazines with beta-ketoester groups. Pyrazolones of formula (XXIX) can be formed from poly(hydrazines), particularly bishydrazines of the formula A5(NHNH2)2, by reaction with a beta-ketoester such as methyl or ethyl acetoacetate. Pyrazolones of formula (XXX) can be formed by reaction of a bis(4-thioacetoacetate), formed from a dathiol and a gamma-chloroacetoacetate, with hydrazine or an alkylhydrazine or arylhydrazine. 
The tetrahydro-1,4-diazepin-5-ones can likewise be synthesised from 1,2-diamines by reaction with a beta-ketoester as described for example in U.S. Pat. No. 4,315,860. In particular, tetrahydrodiazepinones of formula (XXXI) can be synthesised by reaction of bis(beta-aminoamines) of the formula A5(NHCH2CH2NH2)2 with methyl or ethyl acetoacetate or benzoylacetate. Isoxazolone groups can be formed from beta-ketoester groups by reaction with hydroxylamine.
The heterocyclic groups of formula (XII) or (XIII) can for example be hydantoins where X3 or X5 is O, and Z5 is 
for example compounds having groups of formula (XII) can be bis(hydantoins) of the formula: 
or compounds having groups of formula (XIII) can be bis(hydantoins) of the formula: 
where G is a hydrocarbon or polyether chain. Compounds of formula (XXXIV) can be prepared from a hydrocarbon or polyether chain tipped with aldehyde groups, and compounds of formula (XXXV) can be prepared from a hydrocarbon or polyether chain tipped with primary amine groups, as shown by the following reaction schemes: 
Alternatively, the heterocyclic groups of formula (XII) or (XIII) can be analagous 2-thiohydantoin groups in which X3 or X5 is a sulphur atom; these can be prepared by reactions similar to the above using HSCN in place of HNCO. As a further alternative, the heterocyclic groups of formula (XII) can be rhodanine groups of the formula: 
Compounds containing rhodanine groups of formula (XXXVIII) can be prepared from a hydrocarbon or polyether chain tipped with alpha-halo (chloro or bromo)-carboxylic acid groups by reaction with ammonium dithiocarbamate.
Thio-containing unsaturated ester groups of formula (XV) can be formed from a mercaptan and the diester of a diol and an alkynylcarboxylic acid
(HCxe2x89xa1CCO)2A10+R29SHxe2x86x92(R29SCH=CHCOO)2A10.
Thio-containing lactone groups of formula (XIV) can be formed by Michael addition of a bis-mercaptan and a butenolide, followed by oxidation to regenerate the butenolide ring 
where Ar is an arylene group.
The phosphonite ester groups (XVI) or (XVII) or phosphinite ester groups (XVIII) or (XIX) can for example be formed by reaction of a compound or polymer containing free hydroxyl groups with the appropriate organophosphorus chloride. If a cyclic phosphonite ester or phosphinite ester is used, the compound or polymer (B) need only contain one such cyclic phosphonite or phosphinite ester group, since this will react both by Michael-type addition and by ring-opening polymerisation of the Michael adduct to form a crosslinked network. For example, a cyclic phosphonite ester will react with an acrylate-functional polymer containing acrylate groups derived from the reaction of glycidyl groups with acrylic acid as shown below 
where Pm is a polymer residue. Other compounds or polymers containing at least two activated olefinic double bonds such as acrylate groups can be used. The invention therefore includes a coating, adhesive or sealant composition curable by Michael reaction comprising (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound containing a nucleophilic group, characterised in that the nucleophilic group of the Michael donor (B) is selected from cyclic phosphonite esters of the formula: 
and cyclic phosphinite esters of the formula: 
where R51 and R52 each represent an optionally substituted alkyl or aryl group and A16 and A17 each represent an optionally substituted alkylene group. The alkylene group A16 preferably contains 2 to 4 carbon atoms, for example the cyclic phosphonite ester can be ethylene phenylphosphonite, which is readily prepared from C5H5PCl2 and ethylene glycol. Cyclic phosphonite ester groups can in general be readily prepared by hydrolysis of epoxide groups. Particularly preferred Michael donors are those containing two or more cyclic phosphonite ester groups (compounds of formula (XVI) in which R31 and A11 are joined) derived from polyepoxides such as the diglycidyl ether of bisphenol A, a glycidyl acrylate polymer or the diepoxide of 1,7-octadiene. The alkylene group A17 preferably contains 3 to 5 carbon atoms.
The Michael donor compounds containing nucleophilic groups of any of the formulae (V) to (XIX) can in general be used in coating, adhesive or sealant compositions with any Michael acceptor containing at least two activated olefinic double bonds. The Michael acceptor preferably contains doubly activated olefinic double bonds, for example a polymer containing repeating units of formula (I) or a polymer or compound containing groups of formula (II), (III) or (XLV), for most rapid curing. The Michael donor compounds can alternatively be used with known Michael acceptors such as acrylates, for example trimethylolpropane triacrylate, pentaerythritol tri- or tetra-acrylate, the tetra-acrylate of xe2x80x9cCAPA 316xe2x80x9d described above, or an acrylate-tipped oligomer such as a urethane acrylate, melamine acrylate, polyester acrylate or silicone acrylate, to form coating, adhesive or sealant compositions which cure more rapidly, for example 5 or 10 times faster, than known compositions based on Michael donor compounds containing acetoacetate groups. The Michael donor compounds of the present invention can if desired be used in conjunction with known Michael donors such as an acetoacetate, for example an acetoacetate of a polyol or a polymer of acetoacetoxyethyl methacrylate, to give coating, adhesive or sealant compositions which cure faster at ambient temperature than similar compositions based on acetoacetate alone.
Many of the coating, adhesive or sealant compositions of the invention preferably contain a basic catalyst, although Michael donors of formulae (XIV) to (XIX) cure readily without the use of basic catalysts. Tertiary amine catalysts are usually preferred as basic catalysts. These may be strongly basic amines such as diazabicycloundecene or diazabicyclononene or a substituted guanidine for most rapid curing or less basic tertiary amines such as triethylamine. U.S. Pat. No. 4,408,018 teaches that tertiary amines such as triethylamine are not sufficiently alkaline to act as catalysts for Michael curing coating compositions, but we have found that compositions containing a Michael donor having nucleophilic groups of formula (IV) or any of formulae (VII) to (XIII) can cure in less than an hour at ambient temperature when catalysed by triethylamine, particularly if the Michael acceptor contains doubly activated olefinic double bonds. In one preferred embodiment of the invention, a tertiary amine capable of imparting stability against degradation by light, particularly UV light and sunlight, is used as catalyst, preferably as the only basic catalyst. Such an amine is generally a sterically hindered amine such as pentamethylpiperidine or a derivative thereof, particualarly bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate sold commercially under the Trade Mark Tinuvin 292.
An alternative form of preferred catalyst is an alkali metal salt of an activated methylene compound in which the methylene is activated by two adjacent electron-withdrawing groups, for example the sodium or potassium salt of an acetoacetic ester such as ethyl acetoacetate or a malonate diester such as diethyl malonate.
Michael donor compounds containing enamine amide groups of formula (V), enamine beta-carboxylate groups of formula (VI), cyclic enamine amides or beta-carboxylates of formula (VIII) or (IX) or thio-containing ester or lactone groups of formula (XIV) or (XV) have the advantage that they can form coating compositions with Michael acceptors which will cure at ambient temperature without the need for any catalysts, for example in a time of 2 to 3 hours when a Michael acceptor containing doubly activated olefinic double bonds is used. The point of nucleophilic reaction, in contradistinction to other amines which take part in a Michael-type reaction, is not through the N atom. For example, a group of formula (V) reacts with an activated double bond as follows: 
and a group of formula (VI) reacts as follows: 
In general, the nucleophilic groups (IV) to (XIII) take part in the Michael reaction through an activated methylene group, for example in a linkage 
this linkage alternatively may be represented 
The groups of formulae (XIV) and (XV) react with an activated double bond as follows: 
A Michael donor containing phosphonite or phosphinite ester groups, for example those of formulae (XVI) to (XIX), can be used with the same Michael acceptors described above, but the composition is preferably catalysed by a quaternary ammonium halide such as tetrabutylammonium iodide.
The compositions of the invention may contain an organic solvent, for example an aromatic hydrocarbon such as xylene, a ketone such as methyl isobutyl ketone or an ester or etherester such as butyl acetate or methoxypropyl acetate, or they may be solventless. Many of the Michael donors of formulae (IV) to (XIX) are liquids suitable for inclusion in solventless compositions or can be used with liquid Michael acceptors. Similarly, many of the Michael acceptors of formulae (I) to (III) or (XLV) are liquids or can be used with liquid Michael donors. Michael donors of asymmetric molecular structure may be preferred since they are more likely to be liquid or of low Tg and may give rise to tougher cured films.
The compositions of the invention are generally packaged as 2-pack compositions in which the Michael acceptor and the Michael donor are packaged separately and mixed up to 8 hours, preferably up to 2 hours, before use or at the time of application as in the case of coatings applied by twin-feed spray or sealants or adhesives applied from a twin-barrel applicator.
The coating, sealant or adhesive composition may contain additional ingredients. For example, coating compositions will generally contain pigments, for example anticorrosive pigments such as zinc phosphate or sodium zinc molybdate, or colouring and opacifying pigments such as titania, iron oxide or phthalocyanine pigments. Sealant compositions will also generally contain pigments and/or fillers such as calcium carbonate or talc and all types of composition may contain additives such as plasticisers, thixotropes such as silica gel or bentonite clay, or stabilising agents.